1. Field of the Invention
This invention relates in general to earth boring drill bits and in particular to improved means for their lubrication.
2. Description of the Prior Art
Earth drill bit commonly utilize bearing lubrication systems. The successful lubrication of drill bit bearings depends upon an effective seal such as that disclosed in U.S. Pat. No. 3,397,928 issued to Edward M. Galle. The lubrication system typically includes a compensator that equalizes the pressure differential across the seal, as described in U.S. Pats. to Cunningham, Nos. 3,007,750 and 3,137,508. Further, it is advantageous to include a pressure relief valve to limit the internal lubrication system pressure to a selected magnitude above the pressure in the well bore, as disclosed in U.S. Pat. No. 3,476,195 issued to Edward M. Galle.
Though previously known lubrication systems for drill bits have been successful, certain problems persist. The prior art rubber diaphram compensators sometimes become damaged. Their manufacture and assembly requires careful attention. The prior art compensators have numerous areas that require sealing to avoid lubricant loss or entrance of ambient drilling fluids. In general, the prior art compensator systems have a degree of complexity that should be avoided to improve reliability.